Electronic devices, and in particular mobile electronic devices, such as mobile telephones, personal digital assistants, laptop computers, tablet computers, global positioning system receivers, portable games, radios, cameras and camera accessories, and the like are becoming increasingly widely used in many different environments.
It is thus important that said electronic devices including their different parts such as notably the different electronic components and a plurality of cables for electrically connecting said electronic components are made from or coated with polymeric materials that are easy to process into the various parts and that said polymeric materials feature excellent mechanical properties, in particular an excellent balance of high stiffness/high toughness and which are ductile, chemical resistante, flame resistante, moisture resistante.
For example, semi-crystalline polyaryletherketone (PAEK) polymers could be regarded as such polymeric materials as they are known for their exceptional balance of technical properties, namely high melting point, good thermal stability, good stiffness and strength, good toughness and really excellent chemical resistance.
It is generally known that the stiffness of (PAEK) polymers can be increased by adding stiff materials such as reinforcing fillers, in particular glass fibers or carbon fibers but it has the drawback that said reinforced compositions often turn brittle.
It is also worthwhile mentioning that the parts of such mobile devices made from polymeric materials should be able to withstand the rigors of frequent use of such articles, should also comply with the severe fire-protection requirements and can especially meet challenging aesthetic demands such as notably having very low discoloration effects as well showing very minor degradation while not interfering with their intended operability.
Last but not least, the polymeric materials need to be as low in specific gravity as possible, particularly in large mobile units such as laptop computers. In these cases, the use of a glass fiber reinforced resin with a relatively high loading of glass reinforcement (i.e. 20% or more) can become disadvantageous from a unit weight and mobility standpoint as these reinforcements significantly increase the density of the composition relative to the corresponding unfilled polymer. Carbon fiber can mitigate this effect due to its lower density relative to glass fiber, but on the other hand carbon fiber-reinforced plastics have electrical conductivity which limits where in the mobile electronic device such a composition can be used. Furthermore, both glass fibers and carbon fibers when incorporated into a semi-crystalline rigid plastic like PEEK polymer, the commonly result in brittleness which makes the mobile device more vulnerable to breaks during usage. Another disadvantage of reinforcements like glass fibers and carbon fibers is the well known anisotropy effect of these materials. The anisotropic nature of bulk fiber reinforced plastics like glass fiber and carbon fiber, for example is that the composition has non-uniform properties over the various locations of the part, depending on how the fibers are oriented. Strength and stiffness properties are very high in the direction of flow or direction of alignment of the fibers and much weaker properties are realized perpendicular to the orientation of these fibers. The strong anisotropy just mentioned also leads to warpage issues in injection molded parts as different portions or dimensions of the part may shrink differently depending on the state of fiber alignment in that particular direction. There is therefore a need in the art for reinforcements or fillers that do not impart this kind of high anisotropic character to the compositions used in mobile electronic devices.
Thus, there is still a high need for mobile electronic devices comprising at least one part made of a polymeric composition that can overcome the drawbacks mentioned above and wherein said polymeric composition features excellent mechanical properties (and in particular good combination of high stiffness and high toughness, strength, elongation properties and impact resistance), having an excellent balance of stiffness and ductility, good processability, good flow, good thermal stability, low moisture uptake, increased dielectric strength and at the same time causing no discoloration or other degradation phenomena, and wherein said polymeric compositions provide thinner and lighter final parts and mobile electronic devices having improved properties such as more uniform crystallinity, improved ductility, impact resistance, higher tensile and flex modulus as well as strength, thus having the necessary structural integrity and breakage resistance required under the harsh drop testing conditions, having increased dielectric strength and moreover improved aesthetics, especially an improved, lighter color.